Getting a "QXcbConnection: XCB error" everytime I try to open Aegisub

[clearheaded]

Every time I try to open Aegisub it doesn’t open, no response. It’s been like this for a few months.
I tried different versions- pacman -S aegisub, and a few other AUR packages.
I tried pamac build and obviously makepkg.
When I checked journalctl after running aegisub-3.2 in the terminal I got this output:

Apr 18 12:31:18 ** plasmashell[1204]: trying to show an empty dialog
Apr 18 12:31:18 ** kwin_x11[1132]: qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 45135, resource id: 31457793, major code: 14 (GetGeometry), minor code: 0
Apr 18 12:31:18 ** kwin_x11[1132]: qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 45136, resource id: 31457793, major code: 14 (GetGeometry), minor code: 0
Apr 18 12:31:18 ** kwin_x11[1132]: qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 45137, resource id: 31457793, major code: 14 (GetGeometry), minor code: 0

I looked it up and there were a few suggestions regarding qt environment variables so I tried running the following file:

start.sh:

#!/bin/bash
QT_LOGGING_RULES="*.debug=false"
export QT_LOGGING_RULES
exec aegisub-3.2

But again, journalctl:

Apr 18 12:50:50 ** kwin_x11[1132]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 28260, resource id: 12701254, major code: 20 (GetProperty), minor code: 0

There were a few major updates since it started (I believe around Oct-Dec 20’) so I guess it’s not because of outdated packages.
The problem looks to be exclusive to Aegisub but it’s a KWin error and there have been 2-3 updates to the Aegisub package since I it started with no change.

[clearheaded]

SOLVED:
I tried to create a new user and see if it works from there- it did.
After some trial and error with copying and overwriting the contents of the .config folder I’ve managed to find the problem- plasma-localerc.
My plasma-localerc detailed settings (time, currency etc.), the default didn’t. I removed everything except:

[Formats]
LANG=en_US.UTF-8

And it worked.

TL;DR: Deleting the locales but LANG in the ~/.config/plasma-localerc file solved the problem.